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What is desert ? Kinds of Deserts Where Deserts are Found Desertification What are the effects of desertification Reclamation techniques : * Control of sand dunes * Afforestation * Irrigation techniques Conclusion
What is desert ?Desert, an arid region with little or no vegetation. Theword comes from a Latin word meaning abandoned orforsaken, signifying lack of human habitation. Althoughdeserts seem to be uninhabited, some kinds of plants andanimals have adapted to the harsh conditions. People, too,live in or near deserts traditionally as oasis dwellers ornomads. In the 20th century, permanent settlement insome deserts has increased, largely due to improved meansof obtaining water and to such inventions as airconditioning.
The term desert usually refers to areas that, in addition tobeing extremely dry, have high daytime temperatures,particularly in the summer. Many scientists also considerpolar regions to be deserts, since they are arid and sustainlittle or no vegetation.Deserts occupy between 15 and 20 per cent of the earthsland area. They usually receive less than 10 inches (250mm) of precipitation yearly. Precipitation, usually rain,tends to come in a few heavy storms of short duration.Deserts are often bordered by semiarid areas.
Kinds of DesertsThough most scientists who study deserts agree that thereare several types of deserts, they do not agree on how toclassify these types. Some scientists classify desertsaccording to the amount of annual precipitation received.Others classify them according to the types of vegetationand soil present. Still others classify deserts by averagesummer and winter temperatures. In a generalsense, deserts can be categorized by where they are located.
Where Deserts are Found• Rainfall• Temperature• Atmospheric Pressure
DesertificationThe term desertification has been in use since 1949, yet stillthere is no generally accepted definition.Most definitions suggest: • desserts increasing • loss of resource potential • depletion of soil and vegetation cover.Reached wider audience after international concern offamine in West Africa.Affects about 65 million hectares of once agricultural land.Threatens livelihood of 850 million people.Affects more than 100 countries world wide – 27 in Africaalone.
What are the effects of desertificationDesertification reduces the ability of land to supportlife, affecting wild species, domestic animals, agriculturalcrops and people. The reduction in plant cover thataccompanies desertification leads to accelerated soilerosion by wind and water. South Africa losingapproximately 300-400 million tonnes of topsoil every year.As vegetation cover and soil layer are reduced, rain dropimpact and run-off increases.Water is lost off the land instead of soaking into the soil toprovide moisture for plants. Even long-lived plants thatwould normally survive droughts die.
A reduction in plant cover also results in a reduction in thequantity of humus and plant nutrients in the soil, andplant production drops further. As protective plant coverdisappears, floods become more frequent and more severe.Desertification is self-reinforcing, i.e. once the process hasstarted, conditions are set for continual deterioration.
Reclamation techniquesControl of sand dunes is a traditional technologyoriginating from the Ming Dynasty (1368-1644). Floodwater is used to reclaim deserted land, flattening sanddunes, thus controlling wind sand erosion and creatingfarmland.Oil in areas of water shortage.Afforestation is an effective method used to enhance areasthat are affected by drifting sand.Air-seeding allows thedistribution of seeds into regions that would otherwise beecologically unreachable.
Irrigation techniques are inexpensive, the equipment isuser-friedly, plants are guaranteed to grow in allseasons and the permantly wet roots deter termiteinfestations.
Examples :The Mongolian tradition of combating desertification :Involves tree planting which reduces sand movement andprovides.Algeria Green Wall :The "Green Wall" was to halt the advancing desert to the north,creating a barrier of greenery, that protects the steppe from theMoroccan border to that of Tunisia. A total of 3 million hectareswere to be afforested. 160 000 hectares have been only. 160 000hectares which are most often the appearance of large fieldswithered the colors more than gray green
Conclusion : rehabilitation becomes increasinglylengthy and expensive and degradation may reach a threshold beyond which it is reversible and in practical .